Defining a symbol with a value of 0 fails

[Frizzled]

When the value is "0", evaluate().valueOf() becomes a stringed expression instead of a result (confirmed for "GreaterEqual"):

    let math = ["GreaterEqual", "count", 4]
    ce.defineSymbol("count", {value: 0})
    let expr = ce.box(math)
    console.log(expr.evaluate().valueOf()) // "[\"LessEqual\",4,\"countLocal\"]"

When value is anything other than "0" evaluate().valueOf() works as expected:

    let math = ["GreaterEqual", "count", 4]
    ce.defineSymbol("count", {value: 0.000000001})
    let expr = ce.box(math)
    console.log(expr.evaluate().valueOf()) // false

This is also an issue with the newer assignValue()

[arnog]

The issue affected setting a setting to a value of 0, regardless of how it was used. The symbol would end up with no value.